812 INDEX TO THE STRATIGEAPHY OF NORTH AMERICA. 



1 mile soutli of Lambert, Mobile County (elevation about 325 feet), and at Red Bluff, Perdido 

 Bay (just above tide). He bases the following opinions " upon studies of the fQssil flora: 



"Red Bluff is obviously of the same age as the outcrop near Lambert and the same age 

 as the bluffs on Mobile and Pensacola bays. The flora, considered with that of the locaHty near 

 Lambert, is decidedly modern in its facies as compared with the other so-called 'Grand Gulf' 

 outcrops which contain fossil plants, the difficult question being to differentiate between PHo- 

 cene and early Pleistocene. The flora is a mixture of swamp types and those of live-oak bar- 

 rens and indicates climatic conditions such as occur along the Gulf coast to-day, as, for example, 

 on the Santa Rosa Peninsula. 



"In the absence of any American floras for comparison I am disposed to regard the age of 

 the deposits as PHocene, as the species are nearly all extinct and embrace positively identified 

 genera (for example, Trapa) which no longer occur in North America." 



The Lafayette formation was first discriminated by E. W. Hilgard in 1855 and 1856, and 

 named by him in manuscript from Lafayette County, Miss., but the name was not published 

 until 1891. This formation was included in the Orange sand of Safford in Tennessee and the 

 Orange sand cf Hilgard in Mississippi. In 1888 McGee ^^^ applied the name Appomattox to 

 the formation from "the river of typical development in the middle Atlantic slope." McGee's 

 name Appomattox antedates the publication of Hilgard's Lafayette by about three years, 

 but a fact that is perhaps more to the point is that the recent studies of Berry, Lowe, and others 

 around Oxford, Miss., have shown that exposures in Lafayette County, formerly regarded as 

 typical Lafayette formation, are of Wilcox (Eocene) age, rendering very doubtful the pro- 

 priety of applying the name to deposits of probably late Phocene age. The nomenclature has, 

 therefore, been unsettled by the attempt to supplant McGee's Apponaattox and must temporarily 

 be regarded as only tentative. From the evidence now in hand it seems probable that the term 

 Lafayette for the deposits presently to be described will have to be abandoned, and McGee's 

 Appomattox be revived. However, McGee's usage in his paper "The Lafayette formation" 

 will be foUowed here. 



According to McGee,^^"* "In composition the Lafayette formation is a bed of loam, sand, 

 and gravel, with several minor elements, notably kaohn or kaohnic clay, comminuted sOica or . 

 sihceous clay, etc. The clay element of the loam and much of the sand are evidently residua 

 derived from decomposition of a variety of older rocks, the local characters generally reflect- 

 ing the characters of local terranes; the gravel and a part of the sand represent the terranes 

 traversed by the upper reaches of the rivers along which they are found; and the gravel varies in 

 abundance and size with the volume, dechvity, etc., of these rivers. 



"In geographic distribution the Lafayette formation coincides approximately with the 

 Coastal Plain of the southeastern United States. In hypsographic distribution the formation 

 ranges from altitudes of 700 or 800 feet to probably some distance below tide level. 



"In thickness the Lafayette deposits range from a mere veneer over many interstream tracts 

 to 200 feet or more about the mouth of the Mississippi; and in general the thickness varies 

 directly with the volume of neighboring rivers and inversely with the inland extension. The 

 formation has, however, been degraded from considerable areas, particularly along the larger 

 waterways. 



"In structural relation it is separated from the newer Columbia formation by the strongest 

 unconformity of the Coastal Plain, an unconformity representing degradation of probably half 

 the volume of the Lafayette formation and profound trenching of subjacent formations along 

 the larger waterways; and it is separated from all of the underlyiag formations by a note- 

 worthy unconfortnity of such character as to indicate that during pre-Lafayette time the 

 Coastal Plain was a land s'urface and was wrought into a configuration much hke that existing 

 to-day. 



a Unpublished manuscript. 



